A careful reader might have noticed that a lot of common networking-related functionalities are missing from the standard library. For instance, there is no way to deal with IP networks (CIDRs). Let's look at how the ipnetwork crate helps with that. Since we are going to use an external crate, the example has to be in a cargo project. We will need to add it as a dependency to Cargo.toml. Let's start by setting up a project:
$ cargo new --bin ipnetwork-example
This generates a Cargo.toml file that we need to modify to declare our dependency. Once we do that, it should look like this:
[package]
name = "ipnetwork-example"
version = "0.1.0"
authors = ["Foo <foo@bar.com>"]
[dependencies]
ipnetwork = "0.12.7"
Having set up the project, let's look at our main function:
// chapter3/ipnetwork-example/src/main.rs...
